Wednesday 28 April 2010 08.52 EDT
First published on Wednesday 28 April 2010 08.52 EDT

The media finally have the campaign gaffe they were looking for. Gordon Brown has handed it to them on a plate. He has nobody to blame but himself – although that does not appear to stop him trying.

The PR disaster was immediate and obvious. The clip of the prime minister referring to Gillian Duffy as a "bigoted woman" has run all day on television and radio as often as the famous Prescott Punch in 2001. His "apology" on the Jeremy Vine programme served only to make matters worse. Brown looked devastated by what had happened, as well he might, but he seemed to want to blame the broadcasters for airing his words and said he was sorry "if I've said anything like that".

The images of the day tell an extraordinary story: the utterly desolate prime minister, with his head in his hands, while issuing a half apology – then beaming like a man possessed after spending 45 minutes in private with Gillian Duffy. There is no doubt that the first picture reflects Brown's inner feelings.

In terms of damage limitation, the smiling Gordon Brown was almost too much too late. I don't mean to demean him, but he reminded me of my labrador furiously wagging his tail after a good telling off and asking to be loved.

By tomorrow night's debate he must try to look prime ministerial again. Gordon Brown must be longing for this campaign to be over, and soon it will be. But before then dozens of Labour candidates are trying to keep the support of men and women not unlike Duffy. He owes it to them to regain his composure. To sustain its share of the vote and maximise the number of MPs it returns, Labour needs the votes of millions of traditional supporters like Duffy. The party has lost not just hers but potentially thousands of others, who will listen to what she said and find that they agree. Does Brown think they are all bigots too?

The tragedy is that it need not have happened. Gordon Brown handled the initial exchange well. He stayed calm, polite and made some good points in response to what he was asked. It was a wholly unexceptional encounter with a fairly typical member of the public.

Labour candidates – like those of all of other parties – will have encountered voters with genuinely bigoted opinions on doorsteps up and down the country. They are often racist, ill-informed and offensive. Gillian Duffy was none of those things.

Yes, Brown is under pressure. Yes, he knows his campaign is not going well. He is even entitled to his private opinions. But he has been around long enough to know the dangers of microphones that stay live when you've finished saying your piece. What happened was a disaster of his own making. He was wrong to blame the aide who set up the visit, wrong to blame the media for using the dynamite he had placed in their hands, and wrong not to use his first opportunity to apologise with dignity.